1. Field of Invention
The present invention relates to a method for fabricating semiconductor device and word wire. More particularly, the present invention relates to a method for fabricating semiconductor device and word wire with self-aligned silicide (salicide).
2. Description of Related Art
Along with the increase of the integrity of semiconductor devices, the pattern and wire width within the device are also reduced gradually, which causes the resistance at the contact point of gate and wire to increase and creates big RC delay, and further affects the device operation speed. As the resistance of silicide is lower than polysilicon and the thermal stability thereof is higher than common inter-connection material, the silicide can be formed on the gate to reduce the resistance between the gate and the metal connection wire. Since there is no need for a photolithographic process in the fabrication of the silicide, the silicide fabricated by such process is also called self-aligned silicide (salicide).
In another aspect, as the exposed surface portion of the polysilicon may form a native oxide layer, in the fabricating process of salicide, the native oxide layer may lead to bad quality of silicide membrane and increased sheet resistance, such that the efficiency of gate operation is adversely affected. Therefore, when the salicide is formed on the polysilicon gate, usually a pre-sputtering process may be performed on the surface of the polysilicon first to remove the native oxide layer on the surface of polysilicon.
However, while performing the pre-sputtering process, the ions smash against the polysilicon surface and a lot of polysilicon pieces may scatter on the substrate. After the process of the salicide, the polysilicon piece may also form silicide, which can result in a bridge phenomenon among conductors (for example, electrode, wire, etc.). For example, the bridge of the silicide resulted from the polysilicon pieces between two adjacent word wires in the memory cell array can cause electronic defects.